As an example of conventional luminaires, Japanese Utility Model Publication No. 1988-38482 discloses a strip-mounted luminaire to be used for decorative illumination or other purposes. This strip-mounted luminaire includes sockets which are adapted to be arranged on a ribbon cable in such a state that the sockets pierce through the insulation coating of the ribbon cable and are connected to the conductive material of the cable, and electric bulbs to be set in the sockets.
However, the luminaire disclosed in the above publication has a too much height to maintain a good balance, because each socket is designed to removably receive an electric bulb having a single, wedge-type base in such a state that the electric bulb is vertically positioned. Furthermore, as such an electric bulb normally has a vertically positioned filament or a crest-shaped filament, the light distributed in the lengthwise direction of the ribbon cable forms a circle, which is not suitable for in-line illumination.
Luminaires that are arranged in a line and used outdoors for decorative illumination or other purposes have to be waterproof so as to be protected from rain. An example of the luminaires of this type is disclosed in Japanese Patent Laid-open 1995-169313. The luminaire disclosed in this patent calls for sandwiching the cable, along a portion located at a distance from the ends of the cable, between the seat portion and the cap portion(s) of a socket so that the socket supports and electrically connects the cable at the same time. This luminaire also includes a translucent globe made of a transparent synthetic resin. A channel for supporting an O-ring is formed around the neck portion of the translucent globe so that the translucent globe can be fitted in a socket in a waterproof state by forcing the neck portion of the translucent globe into an annular skirt formed on the seat portion of the socket.
The aforementioned luminaire disclosed in Japanese Utility Model Publication No. 1988-38482 is not suitable to be used outdoors, because it is not waterproof. The luminaire disclosed in Japanese Patent Laid-open No. 1995-169313 is provided with a mechanism to attach a globe in a waterproof state and, therefore, may be used outdoors.
On the other hand, the waterproof mechanism for the luminaire disclosed in Japanese Patent Laid-open No. 1995-169313 calls for providing the translucent globe with a neck portion and inserting the neck portion into the skirt of a socket, thereby pressing the O-ring of the neck portion against the inner surface of the skirt. Considering the size of a typical translucent globe with respect to the size of an electric bulb, the diameter of the neck portion is limited. For this reason, the application of the above configuration is limited to such cases that the electric bulb is used at a vertical position. In other words, it is not applicable to cases where the electric bulb is used at a horizontal position, because its horizontal dimension becomes too long. Furthermore, it is difficult to be applied to a socket having an irregular shape.
The structure disclosed in the above patent also calls for snugly inserting a protruding portion that protrudes from the seat portion into a cap portion to affix the cap portion to the seat portion, and inserting pins that protrude from the seat portion into the cable in order to perform the necessary electrical connection. As a result, the depth of the cap portion, i.e. the distance by which the cap portion projects rearward from the cable, becomes excessively long, making it difficult to arrange lamps in a line on the surface of a building or other structure as well as making the position of the lamp too high to be easily mounted.
The above configuration presents another problem in that production costs are high, because its translucent globe has a neck portion and therefore has to be formed by blow molding.
Japanese Utility Model Laid-open No. 1994-23166 discloses another luminaire that has a structure similar to that of Japanese Patent Public Laid-open No. 1995-169313 and presents similar problems. The luminaire disclosed in said publication has a structure that calls for attaching a neck portion of a translucent globe through a cover holder to a cable, to which a socket is connected, so that the translucent globe may be engaged in the socket by hooking a fitting hook between the cable and the neck portion.
However, this structure is not only difficult to be applied to a socket having an irregular shape, but it also presents the danger of the load applied by the fitting hook to the cable causing problems in the cable.
An object of the present invention is to provide a watertight cover mechanism to cover a strip-mounted luminaire in a waterproof state, wherein said watertight cover mechanism is capable of enveloping a socket and an illuminant so as to waterproof them regardless of the shape of the socket or the orientation of the illuminant mounted in the socket, reducing the distance by which the luminaire protrudes from the back of the ribbon cable, permitting the luminaire to be easily mounted on a surface of a building or other structure, and also enabling the production of the translucent globe at a low cost. Another object of the invention is to provided a lighting fixture and an outdoor lighting system adapted to use said watertight cover mechanism for a strip-mounted luminaires